Drive mechanism for grinding wheels



Nov. 15, 1949 'H. F. SHEKELS DRIVE MECHANISM FOR GRINDING WHEELS Filed March 11, 1948 mm mm mf/L, 5 f w W A Patented Nov. 15, 1949 DRIVE MECHANISM FOR GRINDING WHEELS Harold F. Shekels, Pittsburgh, Pa., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application March 11, 1948, Serial No. 14,233

10 Claims.

This invention relates to drive mechanism for grinding wheels and particularly to improved mechanism for varying the rotational speed of grinding wheels to compensate for variations in their diameters.

The most efiicient grinding wheel operation requires that the linear speed of the grinding surface be maintained within an optimum range. As grinding wheels wear, their diameter is reduced. Therefore at constant rotational speed the linear speed of the grinding surface would decrease as the wheel wears. To compensate for this decrease it is customary to increase the rotational speed of the wheel, usually in two or three steps during the life of the wheel.

In belt driven grinding wheels changes in rotational speed of the wheel commonly are accomplished by shifting the belts to different sizes of drive pulleys, several of which may be mounted on the drive axle. Such arrangements have disadvantages that changing the speed is a rather cumbersome operation, and there is no positive means to prevent operation at excessive speeds of unworn wheels having substantially their original diameter.

An object of the present invention is to provide improved variable speed drive mechanism for belt driven grinding wheels wherein speed changes are accomplished by shifting a variable speed gear transmission accessible from the operators station and means are included for positively preventing operation of the wheel at excessive speeds.

A further object of the invention is to provide improved and simplified means for insuring that the linear speed of the grinding surface of a grinding wheel is maintained within the optimum range.

In accomplishing these and other objects of the invention I have provided improved details of structure, a preferred form of which is shown in the accompanying drawing wherein:

igure 1 is a top plan View of a belt driven grinding machine having a drive mechanism embodying features of the present invention, part of the grinding wheel shield being broken away;

Figure 2 is a side elevational view of the grinding machine shown in Figure 1; and

Figure 3 is a vertical sectional view through the grinding wheel shield.

For purposes of illustration, I have shown the improved drive mechanism of the present invention applied to a grinding machine of the swing frame type, although it is apparent that the same mechanism may be employed on other types of belt driven grinding machines, such as stand grinders.

The grinding machine illustrated comprises a main supporting tube H] which carries at one end a yoke I2 and at the other end a motor base l3. The machine is supported by suspension from iuitable means which engage an eye 14. Said eye is fixed at the balance point of the machine to an auxiliary supporting tube [5 which in turn is suitably fixed to main supporting tube l0 and motor base IS.

A motor I6 is mounted on motor base l3 to pivot about a transverse horizontal axis I1. An adjustable linkage I8 is provided for holding said motor in its proper position with respect to the motor base. Said linkage comprises a transverse spindle l9 mounted in suitable bearings 20 on motor base l3 and carrying an internally threaded nut 2|. A threaded longitudinal spindle 22 is engaged with said nut and retained, in adjusted position by lock nuts 23. An eccentric 24 is pivotally mounted at the extremity of spindle 22. A handle 25 is fixed to said eccentric and is rotatably received in bearings 26 fixed to the motor housing. It is seen that the motor may be moved about its pivotal mounting by rotation of handle 25, as for changing belts or working on the motor, and that small adjustments in the position of the motor may be made by adjustment of lock nuts 23 on threaded spindle 22.

Motor [6 drives a set of drive pulleys 21 which are operatively connected by a belt 28 to a set of driven pulleys 29. The latter pulleys are mounted on a grinding wheel axle 30, which is rotatably supported in yoke I2 and carries a grinding wheel 3|. A shield 32 is fixed to yoke 12 and covers the grinding wheel.

In usual operation, the operator grasps the machine by a pair of handles 33 extending rear wardly from the yoke. The under surface of the wheel is employed as the grinding face and is manually lowered against the surface to be ground. Such a machine as just described is standard equipment and is merely an example of 3 the type machine to which the mechanism of the present invention may be applied.

Initially grinding wheel 3| has a standard diameter, for example and operates at a predetermined rotational speed at which the linear speed of the grinding face is within the optimum range. As the wheel is worn away, its diameter becomes less and, to compensate for the loss in linear speed at the grinding face caused by the reduction in diameter, the rotational speed is increased. In accordance with the present invention a variable speed transmission 34 is installed between motor lii and drive pulleys 21 to eifect'speed' changes. Said transmission may be of any suitable known design having a neutral position and three forward speeds, although it is apparent that the mechanism can be simplified by providing only two operating speeds. Since the transmission construction per se is not part of the present invention it-is not shown in detail.

A shift box 35 is fixed to a side wall of shield 32 rearward of axle 33. A shift lever 36 is slidably and pivotally mounted on a pin 37 fixed in said box and extending parallel to axle 3! A gear shifting link 38 is mounted in a pair of axially aligned guide sleeves 39 and 58 fixed to the exterior of shield 32 and the housing of transmission 34 respectively. Link 38 may move longitudinally in said sleeves and also rotate about a longitudinal axis. The end of the link adjacent shift lever 35 .has an integral upstanding segment ll which is connected to the lower end of said shift lever by a free universal joint 42. The opposite end of the link has an integral depending segment d3 which isconnected to a transmission lever A l by free universal joint 45. Universal joints 42 and 45 have sufficient freedom of movement so that linear movement of shift lever 36 may move segment ll in an arcuate path and the resulting arcuate movement of segment 43 may move transmission lever M in a linear path.

The upper face of shift box 35 is apertured to define four positions to which shift lever 35 may be moved. The first is a low speed position 46 forward of the box and away from the grinding wheel. The second is a central neutral position 41. The third is an intermediate speed position 48 rearward of the box and toward the grinding wheel. The fourth is a high speed position 49 forward of the box and toward the grinding wheel and nearer the wheel axis than the intermediate speed position. When the shift lever is moved to any one of these positions, transmission lever 44 automatically is placed in the same position by movement of link 38.

Initially the mechanism is set to the low speed position in which it may be placed at any time. When the grinding wheel becomes partially worn, the motor is stopped and shift lever 36 is moved to the intermediate speed position. When the wheel becomes still further worn, the motor is again stopped and shift lever is moved to the high speed position. Since preferably no clutch is provided, the machine must be stopped before its speed can be changed.

A pair of laterally slidable dogs 5!] and 5| are mounted in shift box 35 and shield 3|. Dog 50 extends into the space shift lever 36 occupies in its intermediate speed position, and dog 5! extends into the space the shift lever occupies in its high speed position. Preferably the dogs are spring urged away from the grinding wheel and have cam faces to be engaged by the shift lever. The side of the latter preferably has a flattened surface 52 to facilitate such engagement. It is seen that when the shift lever is moved to either the intermediate speed position or the high speed position, the corresponding dog is projected into shield 32. If an attempt is made to shift the machine into intermediate speed prematurely before the wheel is sufficiently worn, the end of dog 59 abuts the side of the wheel and prevents such shifting. Likewise if an attempt is made to shift the machine into the high speed position prematurely, the end of dog 5! abuts the side of the wheel and prevents such shifting. As soon as the wheel has worn to the extent that dog 59 can be projected into the shield without engaging the wheel, the machine can be operated at intermediate speed. Similarly when dog M can be projected into the shield, the machine can be operated at high speed.

When it is desired to pivot motor it about axis ll, as for changing belts, shift lever 36 may be moved to a position adjacent shield 32. Then when the motor is pivoted by rotation of handle transmission lever M moves into high speed position and thus allows the motor to pivot inwardly sufficiently for most purposes. If a greater freedom of pivoting is needed, universal joint-42 or 35 may be disjointed.

From the foregoing description, it is seen that I have provided a simple and easily operated mechanism for changing the rotational speed of a grinding wheel to compensate for variations in diameter. The dog mechanism described prevents premature shifting of the mechanism into higher speeds and thereby prevents operation of the wheel at excessive speeds.

While I have shown and described but a single embodiment of the present invention, it is apparent that modifications may arise. Therefore I do not wish to be limited by the disclosure set forth, but only by the scope of the appended claims.

I claim:

1. In a swing frame grinding machine, a frame, means for suspending said frame freely at its balance point from an overhead support, a grinding wheel rotatably mounted in said frame, drive means, belt and pulley means operatively connecting said drive means and said grinding wheel, a variable speed transmission between said drive means and said belt and pulley means for varying the rotational speed of said grinding wheel to' compensate for wear thereon, a shift lever operatively connected with said transmission, and slidable means engageable with said shift lever and being projected into the path of said grinding wheel on shifting of said transmission into higher speeds, said slidable means being adapted to abut said grinding wheel to prevent premature shifting into higher speeds.

2. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, means for driving said grinding wheel, a variable speed transmission between said driving means and said grinding wheel for varying the rotational speed of said grinding wheel to compensate for wear thereon, means for shifting said transmission, and slidable dogs normally occupying the higher speed positions of said shifting means, said dogs being adapted to project into the path of said grinding wheel and to abut said wheel to prevent premature shifting into higher speeds.

3. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, means for driving said grinding wheel, a variable speed transmission between said driving means and said grinding wheel for varyng the rotational speed of said grinding Wheel to compensate for wear thereon, a shift lever operatively connected with said transmission and having a low speed position away from said grinding wheel and a higher speed position toward said grinding wheel, and slidable means normally occupying said higher speed position and being projected into the path of said grinding wheel when said shift lever is moved into the higher speed position, said slidable means being adapted to abut said grinding wheel to prevent premature shifting into the higher speed position.

4. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, means for driving said grinding wheel, a variable speed transmission between said driving means and said grinding wheel for varying the rotational speed of said grinding wheel to compensate for wear thereon and having a low speed, an intermediate speed and a high speed, a shift lever operatively connected with said transmission and having a low speed position away from said grinding wheel, an intermediate speed position toward said grinding wheel and a high speed position toward said grinding wheel but nearer the wheel axis than the intermediate speed position, and slidable means normally occupying the intermediate and high speed positions of said shift lever and being projected into the path of the wheel when said shift lever is moved to one of these positions, said slidable means being adapted to abut said grinding wheel to prevent premature shifting into the intermediate and high speeds.

5. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, means for driving said grinding wheel, a variable speed transmission between said driving means and said grinding wheel for varying the rotational speed of said grinding wheel to compensate for wear thereon and having a low speed, an intermediate speed and a high speed, a shift lever operatively connected with said transmission and having a low speed position away from said grinding wheel, an intermediate speed position toward said grinding wheel and a high speed position toward said grinding wheel but nearer the wheel axis than the intermediate speed position, a slidable dog normally occupying the intermediate speed position of said shift lever, and a second slidable dog normally occupying the high speed position of said shift lever, said dogs having cam faces for engagement with said shift lever and the corresponding dog being projected into the path of said grinding wheel when the shift lever is moved to the intermediate or high speed position, said dogs being adapted to abut said grinding wheel to prevent premature shifting to either of these positions before the grinding wheel has worn sufficiently.

6. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, drive means, belt and pulley means operatively connecting said drive means and said grirr'ding wheel. a variable speed transmission between said drive means and said grinding wheel, a shift box adjacent said grinding wheel, a shift lever mounted in said shift box, a linkage operatively connecting said shift lever and said transmission. said shift lever having a low speed position in said shift box away from said grinding wheel and a higher speed position in said shift box toward said grinding wheel, and means slidable in said shift box and normally occupying said higher speed position, said slidable means being projected into the path of said grinding wheel when said shift lever is moved into the higher speed position and being adapted to abut said grinding wheel to prevent premature shifting into the higher speed position.

7. In a swing frame grinding machine, a frame, means for suspending said frame freely at its balance point from an overhead support, a grindin wheel rotatably mounted on said frame adjacent one end, drive means mounted on said frame adjacent the other end, motion transmitting means operatively connecting said drive means and said grinding wheel and including a variable speed transmission, a shift lever adjacent said grinding wheel operatively connected with said transmission and having a, low speed position away from said grinding wheel and a higher speed position toward said grinding wheel, and slidable means normally occupying said higher speed position and being projected into the path of said grinding wheel when said shift lever is moved into the higher speed position, said slidable means being adapted to abut said grinding wheel to prevent premature shifting into the higher speed position.

8. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, a drive motor spaced from the axis of rotation of said grinding wheel, belt and pulley means operatively connecting said motor and said grinding wheel, a variable speed transmission situated between said motor and said belt and pulley means and being adapted to vary the rotational speed of said grinding wheel to compensate for wear thereon, an operating lever adjacent said grinding wheel, a rod mounted in said frame for pivoting about its longitudinal axis and sliding in the direction of its longitudinal axis and extending from adjacent said transmission to adjacent said operating lever, said rod having end segments extending out of its longitudinal axis, universal joints connecting said segments respectively with said transmission and said operating lever, and means between said operating lever and said grinding wheel preventing premature shifting of said transmission into higher speeds.

9. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, a drive motor spaced from the axis of rotation of said grinding wheel, belt and pulley means operatively connecting said motor and said grinding wheel, a variable speed transmission situated between said motor and said belt and pulley means and being adapted to vary the rotational speed of said grinding wheel to compensate for wear thereon, an operating lever adjacent said grinding wheel and movable toward and away therefrom, a rod mounted in said frame for pivoting about its longitudinal axis and sliding in the direction of its longitudinal axis and extending from adiacent said transmission to adjacent said operating lever, said rod having end segments extending out of its longitudinal axis, universal joints connecting said segments respectively with said transmission and said operating lever, the higher speed positions of said transmission being those in which said operating lever is toward said grinding wheel, and slidable means adapted to engage said grinding wheel and said operating lever preventing premature shifting of said transmission into hi her speeds.

10. In a grinding machine, a frame, a grinding wheel rotatably mounted in said frame, a drive motor spaced from the axis of rotation of said grinding wheel, belt and pulley means operatively connecting said motor and said grinding Wheel, a three speed variable transmission situated between said motor and said belt and pulley means and being adapted to vary the rotational speed of said grinding wheel to compensate for wear thereon, an operating lever adjacent said grinding wheel and having a low speed position away from said grinding wheel, an intermediate speed position toward said grinding wheel, and a high speed position toward said grinding wheel but closer to the axis of rotation than said intermediate speed position, a rod mounted in said frame for pivoting about its longitudinal axis and sliding in the direction of its longitudinal axis and extending from adjacent said transmission to adjacent said operating lever, said rod having end segments extending out of its longitudinal axis, universal joints connecting said segments respectively with said transmission and said operating lever, and slidable dogs normally extending into the intermediate and high speed ositions of said operating lever and adapted to engage said grinding Wheel preventing premature shifting into these speeds.

HAROLD F. SHEKELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Ritz Nov. 27, 1934 

